The present invention relates to an optical fiber holder such as a mechanical splicing or clamping type optical connector for holding optical fibers by vertically sandwiching them.
Conventionally, an optical fiber holder for holding optical fibers by vertically sandwiching them such as a mechanical splicing or clamping type optical connector, is known. As an example of such a mechanical splicing optical connector, one described in Japanese Patent Laid-Open No. 9-318836 is known.
Although optical fibers held by such an optical fiber holder are manufactured to have a predetermined diameter, they inevitably have small diameter errors due to manufacturing errors. For example, a generally widely used optical fiber with a nominal diameter of 125 xcexcm usually has a diameter error of approximately 1 xcexcm to several micrometers.
Since the diameters of optical fibers have small errors in this manner, when a plurality of optical fibers are to be held by vertically sandwiching them with a holder as described above, they sometimes cannot be held reliably. FIGS. 12 to 15 show such a situation. FIG. 12 is a cross-sectional view showing a holder for holding optical fibers F parallel to each other. FIGS. 13 to 15 show a holder for holding optical fibers F by butting them face to face, in which FIG. 13 is a longitudinal sectional view and FIGS. 14 and 15 are cross-sectional views taken at the respective optical fiber F portions. In FIGS. 12 to 15, diameter errors between the optical fibers F and the gap between members 202 and 203 of the holder are emphasized to be larger than they really are.
Each of these holders is comprised of a base member 202 having positioning grooves 209 with V-shaped sections for positioning and aligning the optical fibers F, and a lid member 203 for fixing the optical fibers F placed in the positioning grooves 209 by pressing them against the bottom portions of the positioning grooves 209. When optical fibers F with different diameters are to be sandwiched and held, those with larger diameters are pressed by the lid member 203 against the bottom portions of the positioning groove 209, but those with small diameters form a gap with the lid member 203 (or the bottom portions of the positioning grooves 209). Hence, these optical fibers F are not pressed against the bottom portions of the positioning grooves 209 and accordingly are not held reliably.
If optical fibers F are not reliably held in this manner, as the temperature changes, they may move in the axial direction due to a difference in coefficient of linear expansion between the optical fibers and the respective members. Consequently, a gap is formed between the end faces of the opposing optical fibers F, and the transmission loss increases. If optical fibers F are not reliably held, they undesirably move, even if slightly, within the positioning grooves 209 in the direction of their cross-sections. Then, as shown in FIG. 13, the core positions of the opposing optical fibers F are misaligned from each other, increasing the transmission loss.
In view of the above problems, the present invention has as its object to provide an optical fiber holder which, when holding a plurality of optical fibers by sandwiching them, can reliably hold all the optical fibers even if their diameters may slightly differ due to a size error or the like.
In order to achieve the above problems, an optical fiber holder according to the present invention comprises a base member with a plurality of parallel positioning grooves for positioning and aligning the plurality of optical fibers, a lid member covering the plurality of positioning grooves to fix the plurality of optical fibers, arranged in the positioning grooves, by pressing against bottom portions of the positioning grooves, and small projections with a height from 1 xcexcm to 3 xcexcm inclusive formed on a contacting portion of at least either one of said lid member and said positioning grooves to contact with each of the optical fibers.
Alternatively, an optical fiber holder according to the present invention may comprise a base member with at least one positioning groove for positioning and aligning the opposing optical fibers, a lid member covering the positioning groove, to fix the optical fibers, arranged in the positioning groove to oppose each other, by pressing against a bottom portion of the positioning groove, and small projections with a height from 1 xcexcm to 3 xcexcm inclusive formed on a contacting portion of at least either one of said lid member and said positioning grooves to contact with each of the optical fibers.
With the optical fiber holder according to the present invention, even if the plurality of optical fibers which are arranged parallel to each other or face to face have a diameter error, when the lid member presses the optical fibers against the bottom portion of the positioning groove, the small projections formed on the lid member or positioning groove which comes into contact with the optical fibers deform in accordance with the diameters of the optical fibers. Consequently, each one of the plurality of optical fibers is pressed and reliably held at the bottom portion of the positioning groove without forming a gap with the surface of the lid member or the wall surface of the positioning groove. As a result, the optical fibers are held reliably, so the transmission characteristics do not degrade.
A recess may be formed close to the small projection. When the recess is formed, the deformed portion of the small projection can escape into the recess, and the small projection can deform easily. As a result, the small projection can deform more easily in accordance with the diameter of the optical fiber, and the optical fiber can be held more reliably.
These small projections may be formed on the lid member and may have a semicylindrical shape extending in a direction perpendicular to the direction in which the positioning groove extends. When the small projection is formed with a semicylindrical shape, the contact between the optical fiber in the positioning groove and the small projection starts in the form of point contact, and its contact area increases as the small projection deforms. Since the contact between the optical fiber and small projection starts in the form of point contact, the force acting between the optical fiber and small projection is concentrated on one point, and the small projection tends to deform easily. When deformation of the small projection progresses, the force acting between the optical fiber and small projection is dispersed over a certain area. Therefore, no local excessive load may act on the optical fiber, and no adverse influence is inflicted on the transmission characteristics.
Alternatively, the small projections may arrange on a wall surface of the lid member or positioning groove at an interval of not more than 0.5 mm. When the plurality of small projections are arranged close to each other, the optical fibers can be held reliably upon deformation of the small projections, and stress accompanying the deformation is prevented from locally acting on the optical fibers.
One of the base member and lid member which has the small projections may be made of a member with a larger elasticity than that of the other. When the base member and lid member are made of different materials and the member with the small projection is made of a member softer than that of the other member, the projection itself deforms more easily, while deformation of the remaining member is suppressed. Inconveniences such as occurrence of a nonuniform stress and misalignment of the optical fibers, which are caused by nonuniform deformation of the small projection, can be suppressed.